XLT stands for extra large tall. It is a clothing size that maintains the chest and waist measurements of a standard extra large but adds 1.5 to 2 inches to the torso length and sleeve length. This size accommodates individuals who are generally 6'2" or taller without adding unnecessary width.
Heard on the job
The customer has a 46-inch chest but a long torso, so recommend the XLT instead of the standard XL.